Prism sheets or diffusion sheets used in liquid crystal displays, or optical lenses such as Fresnel lenses or lenticular lenses used in projection TVs have conventionally been produced by injection molding or hot press molding of thermoplastic resins.
These production methods, however, have low productivity because they need a long heating time and a long cooling time during production. Further, in the production methods, optical lenses shrink by heating, and reproducibility of fine structures thereof is poor.
In order to solve these problems, a method is performed in which an active energy ray-curable composition is poured into a mold having a transparent resin base set on an inner surface of the mold, and cured by irradiation with active energy rays.
In recent years, optical lenses have been improved to increase their brightness with development of high brightness displays. For this purpose, a technique of molding high refractive index lenses with a high aromatic ring content has been examined (Patent Literature 1).
A high refractive index cured product prepared from an active energy ray-curable composition with a high aromatic ring content disclosed in Patent Literature 1 is however too rigid. Therefore, fine structures of a cured and molded optical lens are deformed or broken to be damaged, and further, the damaged portions are not restored even after a long period of time. As a result, optical properties such as transmissivity or brightness are problematically impaired.
Another problem is that a rigid optical lens with fine irregularities may damage other components when they are in contact with each other.
In order to solve such problems of a rigid cured product with fine irregularities which is likely to break or to damage other components, it has been suggested that an optical lens with a fine shape that is less likely to break is obtained by devising the shape itself of the optical lens (e.g. Patent Literature 2).
Further, there may be a method of reducing deformation of the shape of a lens for easy restoration of damaged portions. For example, a method for reducing the friction coefficient of a lens surface by adding a slip agent such as silicone oil has been suggested (e.g. Patent Literature 3).